JPH11269305A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition excellent in wet properties and abrasion resistance. SOLUTION: This rubber composition is obtained by (a) mixing 100 pts.wt. polymer component consisting of 30-100 wt.% elastic copolymer having (-70)to 0 deg.C glass transition temperature, and obtained by carrying out solution polymerization of a conjugated diene having 20-60 wt.% styrene content and 15-70 wt.% vinyl content, with an aromatic vinyl compound, with 0-70 wt.% elastomer without the before copolymer, 40-150 pts.wt. silica having 100-300 m<2> /g specific surface area measured by nitrogen adsorption, 0-100 pts.wt. carbon black having 100-300 m<2> /g specific surface area measured by the nitrogen adsorption (with the proviso that the total of the amounts of the silica and the carbon black is 45-165 pts.wt.), 50-200 pts.wt. softening agent for a rubber, and a silane coupling agent, at <130 deg.C temperature for 30 sec to 30 min, (b) further mixing the obtained mixture at 130-180 deg.C for 1-20 min, and (c) adding a vulcanizing agent and a vulcanizing accelerator and further mixing the mixture with the added vulcanizing agent or the like at a temperature not higher than the vulcanizing temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition containing silica.

[0002]

2. Description of the Related Art Conventionally, particularly in the field of tires, silica has been used in place of carbon black as a reinforcing material to meet market demands for wear resistance and low fuel consumption. For the above and performance reasons, silane coupling agents have been combined. In this case, since the rubber composition after vulcanization is cured, the silane coupling agent and silica need to react during processing.

[0003] Thus, for example, diethylene glycol and fatty acids (Rubber Industry Handbook (Fourth Edition)), metal salts of carboxylic acids (Tire Technology International (Tire Technology International))
Technology International), 1995), dithiopropionic acid (JP-A-9-176381), modified silicone oil (JP-A-9-111444), calcium carbonate (JP-A-9-150606), inorganic filler ( International Patent Application No. 95-31888 pamphlet, Japanese Patent Application Laid-Open No. Hei 8-59894, a method of adding sodium thiosulfate (Japanese Patent Application Laid-Open No. Hei 9-118784), a method of treating the surface of silica with silicone oil and then using the same (JP-A-6-248116) has been proposed. However, in these techniques, there is a problem of scorch and a problem of performance such as a sufficient improvement in strength due to the use of the auxiliary agent, and there is a problem that the solution is not sufficiently solved for practical use.

Accordingly, for example, Japanese Patent No. 2635882, Japanese Patent Application Laid-Open No. 8-259735, and Japanese Patent Application Laid-Open No. 8-259
No. 736 and JP-A-8-259739 disclose methods of performing kneading in two stages. According to these methods, both workability and silica performance (rolling resistance, wet performance) are compatible. Is insufficient.

[0005]

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a rubber composition in which a silane coupling agent and silica efficiently react with each other to improve wet performance and abrasion resistance. It is in.

[0006]

According to the present invention, there are provided (a) a glass transition temperature of -70 to 0 ° C and a styrene content of 20 to 60.
% By weight, a solution-polymerized elastic copolymer of a conjugated diene and an aromatic vinyl compound having a vinyl content of 15 to 70% by weight.
100% by weight and an elastomer other than the copolymer 0
40 to 150 parts by weight of silica having a nitrogen adsorption specific surface area of 100 to 300 m ² / g, and 100 to 300 parts by weight of a polymer component consisting of
0 to 100 parts by weight of carbon black of 300 to 300 m ² / g (the total amount of silica and carbon black is 45 to 165 parts by weight based on 100 parts by weight of the copolymer), and 50 to 200 parts by weight of a rubber softener And the silane coupling agent are mixed at a temperature lower than 130 ° C. for 30 seconds to 30 minutes, and then (b) mixed at 130 to 180 ° C. for 1 to 20 minutes, and then (c) a vulcanizing agent and a vulcanization accelerator are added. And a rubber composition obtained by mixing at a temperature below the vulcanization temperature.

In this case, it is preferable that after the mixing in the step (a), the temperature of the rubber mixture is cooled to 100 ° C. or less, and then the mixing in the step (b) is performed.

The silane coupling agent is represented by the formula (1):
Z—R—S _n —R—Z or formula (2) Z—R—SH (wherein, in formulas (1) and (2), R is a divalent hydrocarbon group having 1 to 18 carbon atoms, and n is 2 to 2) An integer of 8, and Z is -Si (R ¹ ) ₂ R
² , —SiR ¹ (R ² ) ₂ or —Si (R ² ) ₃ (where R ¹ is an alkyl group having 1 to 4 carbon atoms, cyclohexyl group or phenyl group, and R ² is an alkoxy group having 1 to 8 carbon atoms) Or a cycloalkoxy group having 5 to 8 carbon atoms))
Preferably,

Further, the elastomer may be selected from natural rubber, isoprene rubber and butadiene rubber, butyl rubber and p-
It is preferably at least one selected from the group consisting of brominated methylstyrene / isobutylene copolymer.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, first, as step (a), the glass transition temperature is -70 to 0 ° C, the styrene content is 20 to 60% by weight, and the vinyl content is 15 to 70%.
Nitrogen adsorption on 100% by weight of a polymer component consisting of 30 to 100% by weight of a solution-polymerized elastic copolymer of a conjugated diene and an aromatic vinyl compound and 0 to 70% by weight of an elastomer other than the copolymer. Specific surface area is 100 ~
Silica 40-150 parts by weight of 300m ² / g, carbon black 5-100 parts by weight of the nitrogen adsorption specific surface area of 100 to 300 m ² / g, the rubber softener 50 to 200 parts by weight of a silane coupling agent 130 ° C. Less than 3
Mix for 0 seconds to 30 minutes. This mixing step (a) is mainly performed to mutually disperse the polymer, silica and the silane coupling agent.

In the present invention, the rubber component comprising 30 to 100% by weight of the copolymer and 0 to 70% by weight of the elastomer is used from the viewpoint of improving abrasion resistance and wet performance.

First, the rubber component of the present invention has a glass transition temperature of -70 to 0 ° C and a styrene content of 20 to 60.
A solution-polymerized elastic copolymer of a conjugated diene and an aromatic vinyl compound having a vinyl content of 15 to 70% by weight (hereinafter, also simply referred to as “copolymer”) will be described.

The copolymer used in the present invention is obtained by subjecting a conjugated diene such as butadiene or isoprene and an aromatic vinyl compound such as styrene to solution polymerization in a conventional manner. This copolymer may have a styrene content of 20 to 60% by weight and a vinyl content of 15 to 70% by weight from the viewpoint of wet performance.

The glass transition temperature of the copolymer is as follows:
The temperature may be −70 to 0 ° C., but is preferably −40 to 0 ° C. from the viewpoint of achieving both wet performance and wear resistance.

The elastomer is compounded for improving abrasion resistance and strength (or maintaining and improving the performance). Natural elastomer, isoprene rubber and butadiene rubber, butyl rubber and p-methylstyrene / isobutylene copolymer are used. It is preferably at least one selected from the group consisting of coalesced bromides.

In the present invention, as described above, 30 to 100% by weight of the copolymer and 0 to 70% of the elastomer are used.
A polymer component consisting of% by weight is used.

The silica used in the present invention has a nitrogen adsorption specific surface area of 100 to 100 from the viewpoint of imparting a reinforcing effect, not deteriorating dispersibility, and suppressing heat generation.
It may be a 300 meters ² / g, further, from the viewpoint of abrasion resistance (strength), preferably from 100 to 250 m ² / g.

The amount of the silica in the present invention may be within a range that does not impair the effects of the present invention, and may be 40 to 150 parts by weight based on 100 parts by weight of the copolymer.

The carbon black used in the present invention may have a nitrogen adsorption specific surface area of 100 to 300 m ² / g in terms of abrasion resistance, and 100 to 250 m ^{2 in} terms of high strength and workability. ^It is preferably ² / g.

In the present invention, the amount of the carbon black is from 0 to 100 parts by weight of the copolymer.
100 parts by weight is sufficient, but from the point of abrasion resistance,
It is preferably from 10 to 100 parts by weight.

However, from the viewpoint of abrasion resistance, wet performance and processability, the total amount of silica and carbon black is 45 to 165 parts by weight based on 100 parts by weight of the copolymer.

The rubber softener used in the present invention is not particularly limited as long as it has been conventionally used in the field of rubber compositions. For example, paraffin-based process oils, naphthene-based process oils, and aromatic-based softeners Process oil, special process oil, etc.
These can be used alone or in any combination.

The compounding amount of the rubber softener may be 50 to 200 parts by weight based on 100 parts by weight of the copolymer in view of processability and performance. Therefore, it is preferably 50 to 150 parts by weight.

Here, the tread rubber used for high performance tires and racing tires, in particular, employs a composition in which a filler such as silica is highly filled and a rubber softener such as aroma oil is also highly filled. In the case of these blends, it is necessary to apply high shear during kneading and to raise the temperature to increase the dispersibility of silica and the reaction of the silane coupling agent. However, these compounds contain a large amount of a softening agent for rubber, so that when heated to a high temperature, the viscosity of the rubber sharply decreases, and almost no shear is applied during kneading, and the dispersion of the filler is insufficient. . On the other hand, according to the present invention, the reaction between the silica and the silane coupling agent can be sufficiently completed while maintaining the dispersion of the filler such as silica high in the rubber composition.

Next, the silane coupling agent used in the present invention may be any one which is conventionally used in a rubber composition together with silica, for example, the formula (1): Z
-R-S _n -R-Z, wherein (2): Z-R- SH, wherein (3): Z-R- NH 2 ( e.g., N-beta (aminoethyl) .gamma.-aminopropyltrimethoxysilane) , Formula (4): Z—CH 2CH ₂ (for example, vinyl tris (β-methoxyethoxysilane), vinyl triethoxy silane) and Formula (5): Z—R—Cl (for example, vinyl trichlorosilane) (Formula (1) ) To (5), R is a divalent hydrocarbon group having 1 to 18 carbon atoms, n is an integer of 2 to 8,
Is ^{_{-Si (R 1) 2 R 2}} , -SiR 1 (R 2) 2 or -Si (R ²⁾ ₃ (provided that, R ¹ represents an alkyl group having 1 to 4 carbon atoms, cyclohexyl or phenyl group, R ² Is an alkoxy group having 1 to 8 carbon atoms or a cycloalkoxy group having 5 to 8 carbon atoms), and from the viewpoint of performance and processability, the above formula (1): _{Z-R-S n -R-} Z or (2) preferably used Z-R-SH silane coupling agent represented by.

Examples of the silane coupling agent represented by the formula (1) include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, and bis (2-triethoxysilylpropyl). ) Tetrasulfide and the like.

Examples of the silane coupling agent represented by the formula (2) include 3-mercaptopropyltriethoxysilane, 2-mercaptopropyltrimethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and the like. Is raised.

Of these, bis (3-triethoxysilylpropyl) tetrasulfide is preferably used from the viewpoints of performance improvement and processability.

The compounding amount of the silane coupling agent may be within a range that does not impair the effects of the present invention. However, from the viewpoint of performance improvement and processability, the amount of the silane coupling agent is 5 to 20% by weight of the silica. It is preferable that the amount is 5% to 10% by weight in view of cost.

In the present invention, the above components are first mixed in step (a). As the mixing means at this time, a conventional mechanical mixing means such as a Banbury mixer or a kneader can be used.

The mixing temperature is preferably lower than 130 ° C. so that the viscosity of the rubber composition during mixing does not decrease and sufficient dispersion of the filler is not hindered. Particularly preferred is 120 ° C.

The mixing time is preferably from 30 seconds to 30 minutes from the viewpoint of dispersibility, and more preferably from 30 seconds to 20 minutes from the viewpoint of cost.

Next, in the present invention, the rubber mixture A obtained in the step (a) is further mixed in the step (b). This mixing step (b) is performed for chemically bonding the silica and the silane coupling agent.

The mixing temperature in the step (b) may be 130 to 180 ° C. from the viewpoint of reactivity.
The temperature is from 145 to 165 ° C. from the viewpoint that the characteristics of silica are sufficiently exhibited, and the crosslinking reaction is accelerated by sulfur atoms that can be contained in the silane coupling agent, thereby preventing gelation and deterioration of the rubber skin. Is particularly preferred.

The mixing time is preferably from 1 to 20 minutes from the viewpoint of reactivity, and more preferably from 1 to 15 minutes from the viewpoint of preventing gelation.

The mixing means in the step (b) may be the same as that used in the step (a).

Finally, in the present invention, in the step (c), a vulcanizing agent and a vulcanization accelerator (vulcanizing system) are added to the rubber composition B obtained in the step (b) and mixed.
This mixing step (c) is mainly performed for dispersing the vulcanizing agent.

The mixing means at this time includes a Banbury mixer, a kneader, a roll and the like.

The mixing temperature in the mixing step (c) may be a temperature not higher than the vulcanization temperature from the viewpoint that rubber scorch does not occur. Temperature below the vulcanization temperature, the type of the copolymer used, the type of diene elastomer,
Although it depends on the amount and type of vulcanizing agent, it is usually 80 to
The temperature may be 120 ° C.

Further, the mixing time is preferably from 1 to 20 minutes from the viewpoint of dispersibility, and more preferably from 1 to 15 minutes from the viewpoint of cost.

In the rubber composition of the present invention, in addition to the above components, fillers such as talc and clay, tackifiers such as coumarone indene resin, rosin resin, cyclopentadiene resin, sulfur Vulcanizing agents such as peroxides, vulcanization accelerators, stearic acid, vulcanization aids such as zinc oxide, antioxidants, and the like are appropriately blended as necessary within a range not to impair the effects of the present invention. be able to. However, when these components are blended, steps (a) to
Although it may be blended at any stage of (b), it is preferred to blend in the step (b) in that it does not hinder the mixing of the silica, the polymer and the silane coupling agent.

The rubber composition obtained by the above method preferably has a ratio (M300 / M100) of tensile strength M300 to M100 after vulcanization (M300 / M100) of 4 or more from the viewpoint of reaction between silica and a silane coupling agent. preferable.
The upper limit is not particularly limited, but is usually about 6. The tensile strength in the present invention is defined by JIS
It refers to a value measured in accordance with K6301.

The rubber composition of the present invention can be applied to, for example, treads and shoe soles of tires from the viewpoint of wet performance and abrasion resistance. In particular, the present invention also relates to a tire having a tread comprising the rubber composition of the present invention. Above all, it is preferably applied to racing tires because it contains a large amount of silica and a softening agent for rubber.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0045]

EXAMPLES Table 1 shows Examples 1 to 3 and Comparative Examples 1 to 1.
5 shows the components used and the amounts of the components used.

Examples 1 to 3 According to the mixing ratios shown in Table 2, each step (a) of the present invention was carried out.
The rubber compositions 1 to 4 were obtained by the method of the present invention under the conditions shown in Table 2 with the conditions (c) to (c). In steps (a) and (b), a BR type Banbury mixer was used, and in step (c), an open roll was used. Step (a)
The resulting rubber mixture A was allowed to cool to room temperature, and then subjected to step (b).

Then, the obtained rubber compositions 1 to 3 were mixed with 17
Vulcanized products 1 to 3 were obtained by press vulcanization at 0 ° C. for 20 minutes, and evaluated by the following test methods. Table 2 shows the results.

[Test Method] Tensile test: M10 according to JIS K6301
0, M300, T _B and E _B were measured.

Hardness test: Hardness was measured by the following method.

Abrasion test: Using a Lambourn abrasion tester, temperature 23 ° C., slip rate 20%, test time 5 minutes,
Load weight 2kg. The amount of loss was calculated by volume under the condition of the amount of falling sand of 20 g / min.
Abrasion index = (Loss of Comparative Example 1 / Loss of each Example) ×
The wear index was determined according to 100.

Wet skid test: Using a portable skid tester manufactured by Stanley, ASTM E-
The wet skid index was determined by the formula: wet skid index = (index of each example / index of comparative example 1) × 100 according to the method of 303-83. The higher the wet skid index, the better the wet skid resistance.

Comparative Examples 1 and 2 Comparative rubber compositions 1 and 2 were prepared in the same manner as in Example 1 except that step (b) was not performed and the conditions shown in Table 2 were used.
Was manufactured and the same test as in the example was performed. Table 2 shows the results
Shown in

Comparative Examples 3 to 5 Comparative rubber compositions 3 to 5 were produced in the same manner as in Example 1 except that the mixing ratios and conditions shown in Table 2 were changed, and the same tests as in the examples were performed. Table 2 shows the results.

[0054]

[Table 1]

[0055]

[Table 2]

Comparative Examples 6 to 8 Comparative rubber compositions 6 to 8 were obtained in the same manner as in Example 1 except that the mixing ratios shown in Table 3 were changed, and the same tests as in the examples were performed. Table 3 shows the results. Table 3 shows the results of Example 1 for comparison.

[0057]

[Table 3]

Comparative Examples 9 to 11 Comparative rubber compositions 9 to 11 were obtained in the same manner as in Comparative Example 1 with the blending ratios of Comparative Examples 6 to 8, and the same tests as in Examples were performed. Table 4 shows the results.

[0059]

[Table 4]

Table 4 shows that the performance of the obtained rubber composition is not improved even if the mixing ratio is changed within a range not satisfying the requirements of the present invention.

[0061]

According to the present invention, it is possible to obtain a rubber composition in which a silane coupling agent and silica efficiently react with each other to achieve both wet performance and abrasion resistance.

Continued on the front page (72) Inventor Ikuyo Tamura 3-22-13-205 Kita-Aoki, Higashinada-ku, Kobe-shi, Hyogo (72) Inventor Noriko Yagi 5-11-16, Owada, Nishiyodogawa-ku, Osaka-shi

Claims (4)

[Claims] (A) a glass transition temperature of -70 to 0 ° C.
Having a styrene content of 20 to 60% by weight and a vinyl content of 1
5 to 70% by weight of a polymer component composed of 30 to 100% by weight of a solution-polymerized elastic copolymer of a conjugated diene and an aromatic vinyl compound and 0 to 70% by weight of an elastomer other than the elastic copolymer is used. contrast, the nitrogen adsorption specific surface area of silica 40-150 parts by weight of 100 to 300 m ² / g, nitrogen adsorption specific surface area of carbon black 0-100 parts by weight of 100 to 300 m ² / g (where silica and carbon black The total amount is 45 to 165 parts by weight based on 100 parts by weight of the copolymer), and the rubber softener 50 to 20 is used.
After mixing 0 parts by weight and the silane coupling agent at a temperature lower than 130 ° C. for 30 seconds to 30 minutes, (b) 130
A rubber composition obtained by mixing at ~ 180 ° C for 1-20 minutes, and then adding (c) a vulcanizing agent and a vulcanization accelerator and mixing at a temperature lower than the vulcanization temperature. 2. The rubber composition according to claim 1, wherein after the mixing in the step (a), the temperature of the rubber mixture is cooled to 100 ° C. or less, and then the mixing in the step (b) is performed. 3. The method according to claim 1, wherein the silane coupling agent is of the formula (1): Z-
R—S _n —R—Z or formula (2) Z—R—SH (wherein, in formulas (1) and (2), R is a divalent hydrocarbon group having 1 to 18 carbon atoms; An integer, Z is -Si (R ¹ ) ₂ R
² , —SiR ¹ (R ² ) ₂ or —Si (R ² ) ₃ (where R ¹ is an alkyl group having 1 to 4 carbon atoms, cyclohexyl group or phenyl group, and R ² is an alkoxy group having 1 to 8 carbon atoms) Or a cycloalkoxy group having 5 to 8 carbon atoms))
The rubber composition according to claim 1, wherein 4. The elastomer according to claim 1, wherein the elastomer is at least one selected from the group consisting of natural rubber, isoprene rubber and butadiene rubber, butyl rubber and bromide of p-methylstyrene / isobutylene copolymer. A rubber composition according to any one of the above.